Die Kinetik heterogener Elektronentransferreaktionen in polaren Lösungsmitteln

Multiple Mechanisms for Electron Transfer at Metal/Self‐Assembled Monolayer/Room‐Temperature Ionic Liquid Junctions: Dynamical Arrest versus Frictional Control and Non‐Adiabaticity

“…General assay: We took advantage of using modern, well-established electrochemical methodologies [40][41][42][43] (two complementary approaches, see below) and related analyses [26][27][28][29] to extract intrinsic ET rate constants under standard conditions (i.e., at zero overpotential, DG 0 = 0), and at electrode potentials different from the standard value of our redox probe, [Fe(Cp) 2 ] 0/ + , at DG 0 0. Fast-scan cyclic and steady-state voltammetry, global computer-aided and Nicholsons basic two-point fitting, SavØants deconvolution procedure and Gaussian curve analyses were applied to determine heterogeneous rate constants and/or reorganisation energies, respectively (see the Experimental Section for details).…”

“…[40,42,43] For this purpose, background-subtracted voltammograms were converted into the sigmoidal-shaped curves by a semi-integral convolution technique and rate constants at different overvoltages were calculated by using Equation (8): [40,42] k EXP ðEÞ ¼ D in which i(E) is the real experimental current, I(E) is the convoluted current and I lim is the convoluted limiting current (I lim = nFAD À1/2 C 0 ). Next, we transformed experimental heterogeneous rate constants into the uni-A C H T U N G T R E N N U N G molecular intrinsic constants by using the formalism developed by Weaver et al and Fawcett et al [26][27][28][29] In a classical case in which the pre-equilibrium step is not accompanied by the notable adsorption of reactant species on the electrode surface (freely diffusing regime) and the charge-transfer step is not accompanied by considerable inner-sphere reorganisation, the experimental standard heterogeneous rate constant can be presented as a product of two components as shown in Equation (9): [28,29] …”

“…In the case of c (n + 1) = 18, the fitting procedure yielded l 0 = (1.0 AE 0.1) eV, a value that is close to that theoretically deduced and experimentally found for the ferrocene/ferrocenium couple in aqueous and other molecular (polar) solvents. [21,22,26,27] We note that neither the classical Marcus equation (see the Supporting Information), [18,20] nor its extension to the three-phase (metal/ SAM/solution) configuration, [47] can be initially applied in the case of RTILs as a reaction medium. At least one reason for this is the important contribution of slow translational degrees of freedom in actual dielectric polarisation properties.…”

Linear Sweep and Cyclic Voltammetry

“…The characteristic size of electrodes is conventionally a few millimeters (radius for a planar disk) as a maximum. The current minimum for disk electrodes is in the nanometer region [36], where, however, reproducibility may be a problem and the exact determination of the electroactive area is difficult [37].…”

Molecular Electrochemistry of Cyclophanes

“…This reaction is often used as a standard for potentials in nonaqueous solvents [10] and reversibility, although it has neither an infinite electron transfer rate [62] nor is its oxidation product stable on a long time scale [63]. Nevertheless, in CV most often the reverse peak is observed, even in its derivatives.…”